Paracrine signals from the mouse conceptus are not required for the normal progression of decidualization.

Department of Physiology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901, USA.

Abstract

The purpose of this study was to determine whether the conceptus directs the formation of a tight- and adherens-dependent permeability barrier formed by the primary decidual zone and normal progression of decidual cell differentiation during embryo implantation. Four artificial models of decidualization were used, some apparently more physiological than others. The results show that both the formation of the permeability barrier and decidual cell differentiation of three of the artificial models were quite different from that of pregnant uteri. One artificial model of decidualization, namely pseudopregnant animals receiving concanavalin A-coated Sepharose bead transfers on d 2.5 of pseudopregnancy, better recapitulated the decidual changes that occur in the pregnant uterus undergoing decidualization. This included the formation of a primary decidual zone-like permeability barrier and decidual growth. This model also exhibited similar temporal changes of the expression of genes involved in decidualization that are markers of decidual cell differentiation. Overall, the results of this study indicate that some models of inducing decidualization artificially produce responses that are more similar to those occurring in the pregnant uterus, whereas others are quite different. More importantly, the results suggest that concanavalin A-coated Sepharose beads can provide an equivalent stimulus as the trophectoderm to cause the formation of the primary decidual zone permeability barrier.

Timeline of the models of decidualization used in this study. A, Normal pregnant animals; B, Pseudo-BID model; C, Ovx-OID model; D and E, Preg-OID (D) and Pseudo-OID (E) models. Solid black areas indicate periods when the lights were off, and the open areas periods when the lights were on. Days indicated are days of pregnancy (DOP) and days of pseudopregnancy (DOPP) for pregnant and pseudopregnant mice. Days for the Ovx-OID model are equivalent days of pseudopregnancy.

Decidualization in the various models used in this study. A and B, Representative photomicrographs (n = 3) of immunohistochemical localization of CTNNB1 and TJP1 in the endometrium during the early phase of decidualization in the decidua and deciduoma in mice on d 5.5 in pregnant, Pseudo-BID, and Ovx-OID models (A) or d 4.5 in Preg-OID and Pseudo-BID (B) models; C, representative photomicrographs of uterine cross-sections collected the morning of d 7.5; D, graph showing mean (±sem, n = 4–6) cross-sectional areas of endometrial tissue from d 4.5–8.5. Bars with different letters at each time point are significantly (P < 0.05) different. am, Antimesometrial side; b, bead; e, embryo. Scale bar in A, 100 μm for all panels in panels A and B.